Drugs flushed into the environment could be cause of wildlife decline

New studies show antidepressants causing starlings to feed less and contraceptive drugs reducing fish populations in lakes.

New work reveals that an anti-depressant reduces feeding in starlings and that a contraceptive drug slashes fish populations in lakes

Potent pharmaceuticals flushed into the environment via human and animal sewage could be a hidden cause of the global wildlife crisis, according to new research. The scientists warn that worldwide use of the drugs, which are designed to be biologically active at low concentrations, is rising rapidly but that too little is currently known about their effect on the natural world.

Studies of the effect of pharmaceutical contamination on wildlife are rare but new work published on Monday reveals that an anti-depressant reduces feeding in starlings and that a contraceptive drug slashes fish populations in lakes.

"With thousands of pharmaceuticals in use globally, they have the potential to have potent effects on wildlife and ecosystems," said Kathryn Arnold, at the University of York, who edited a special issue of the journal Philosophical Transactions of the Royal Society B. "Given the many benefits of pharmaceuticals, there is a need for science to deliver better estimates of the environmental risks they pose."

She said: "Given that populations of many species living in human-altered landscapes are declining for reasons that cannot be fully explained, we believe that it is time to explore emerging challenges," such as pharmaceutical pollution.

A few dramatic examples of wildlife harmed by drug contamination have been discovered previously, including male fish being feminised by the synthetic hormones used in birth-control pills and vultures in India being virtually wiped out by an anti-inflammatory drug given to the cattle on whose carcasses they feed. Inter-sex frogs have also recently been found in urban ponds contaminated with wastewater.

But because the pharmaceuticals are not designed to kill - unlike pesticides - the damage caused to wildlife can be more subtle.

Another new study, led by Karen Kidd at the University of New Brunswick, showed synthetic oestrogen used in the birth control pill not only wiped out fathead minnows in lakes used for experiments in Ontario, but also seriously disrupted the whole ecosystem. The lakes' top predator - trout - declined by 23-42%, due to the loss of the minnow and other prey, while insects increased as they were no longer being eaten by the minnows.

Amphibians are suffering the hardest in the global biodiversity decline and Cecilia Berg, at Uppsala University, and colleagues reported that a number of hormonally active pharmaceuticals harm reproduction in amphibians at concentrations that occur in natural waters.

The most environmentally dangerous drugs are identified in a paper by Anette Küster and Nicole Adler, both at Germany's Federal Environment Agency. "For human medicinal products, hormones, antibiotics, [painkillers], antidepressants and [anti-cancer drugs] indicated an environmental risk," they said. For veterinary drugs, hormones, antibiotics and parasiticides were highlighted.

Pharmaceuticals can contaminate the environment through discharges from drug factories, as well as through sewage. Professor Joakim Larsson, at the University of Gothenburg, found that drug levels in effluents can even exceed those found in the blood of people taking medication.

Larsson cited antibiotic pollution coming from factories in China, India, Pakistan, Korea, Denmark, Norway and Croatia. "Although pollution from manufacturing is less widespread, discharges that promote the development of drug-resistant microorganisms can still have global consequences." He also documented antidepressant pollution from factories in Switzerland, Israel and Spain and "narcotic opioid" pollution in the US.

The use of pharmaceuticals is rising with increases in the human population and the livestock it keeps. Environmental exposure is also rising as sewage is increasingly used to irrigate or fertilise farmland. In the US, for example, about 4m tonnes of dry sewage biosolids are applied to land each year.